Perhaps this is the right place to comment on solar tilt angles (for solar PV and solar thermal). Actually the apparent position of the sun at any given time is not of much interest. For a fixed tilt angle, you need to know the best tilt angle for the year, the season, the month, ... for a particular day. It is NOT the tilt angle at solar noon: in fact the best tilt angle is always higher. They are NOT simply latitude for annual or spring, fall; or latitude - 15 for summer, latitude + 15 for winter.
Here is a sample (Doc): but attachment does not appear; perhaps it is too long.
Contact by email for sample: send lat., long. and I will provide your best tilt angles.
Soon I will have a URL for you to visit.
Here is my updated URL: http://home.comcast.net/~peter.jackieSelect "Photos" - zoom for better quality

Can you cut it up and paste the article? Or a link to a website of it?

NREL Redbook, download the one for your state to see solar radiation values

http://rredc.nrel.gov/solar/pubs/redbook/

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Wy:
I use the published NREL color charts, taking the average from each monthly chart for each season.
Peter

I am trying to attach my chart, but its size is too large.
Contact me and I will email it.
peter07@comcast.net